+/+…when timing is critical
C9825B
Low EMI Clock Generator for Intel 133MHz/3DIMM Chipset Systems
Preliminary
Serial Control Registers
NOTE: The Pin# column lists the affected pin number where applicable. The @Pup column gives the state at true
power up. Bytes are set to the values shown only on true power up.
Following the acknowledge of the Address Byte, two additional bytes must be sent:
1) “Command Code “ byte, and
2) “Byte Count” byte.
Although the data (bits) in these two bytes are considered “don’t care”; they must be sent and will be acknowledged.
After the Command Code and the Count bytes have been acknowledged, the below described sequence (Byte 0, Byte 1,
and Byte2) will be valid and acknowledged.
Byte 0: CPU Clock Register (1=Enable, 0=Disable)
Byte 1: SDRAM Clock Register (1=Enable, 0=Disable)
Bit
7
6
5
4
@Pup
Pin#
Description
Bit
7
6
5
4
3
2
1
0
@Pup
Pin#
Description
RESERVED (drive to “0”)
RESERVED (drive to “0”)
SDRAM5
SDRAM4
SDRAM3
SDRAM2
SDRAM1
SDRAM0
0
0
0
0
0
-
-
-
-
-
Sel3 frequency selector
Sel2 frequency selector
Sel1 frequency selector
Sel0 frequency selector
1 = Spread Spectrum Enabled
0 = Spread Spectrum Disabled
DOT
1
1
1
1
1
1
1
1
-
-
-
-
-
-
-
-
3
2
1
0
1
1
0
28
27
-
USB
High enables bit(7:4) selectors.
Byte 3: Reserved Register
Byte 2: SDRAM Clock Register (1=Enable, 0=Disable)
Bit
7
6
5
4
3
2
1
0
@Pup
Pin#
Description
RESERVED
High puts the device in TEST mode.
RESERVED
RESERVED
RESERVED
RESERVED
1 = PD#, 0 = TS#
0 = SDRAM runs at 100MHz
1= SDRAM runs at 133.3MHz
Bit
7
@Pup
Pin#
10
-
Description
3V66-2
0
0
0
0
0
0
1
0
-
-
-
-
-
-
-
-
1
1
1
1
1
1
1
0
6
5
4
3
2
1
0
RESERVED (drive to “0”)
RESERVED (drive to “0”)
SDRAM8
SDRAM7
SDRAM6
-
29
30
31
13
-
PCI1
Reserved
Byte 5: SSCG Control Register
Byte 4: PCI Clock Register (1=Enable, 0=Disable)
Bit
7
6
5
4
3
2
1
0
@Pup
Pin#
Description
Spread Mode (0=down, 1=center)
Selects spread bandwidth. Ref. Table 4
Selects spread bandwidth. Ref. Table 4
Reserved
Reserved
Reserved
Reserved
Reserved
Bit
7
6
5
4
3
2
1
0
@Pup
Pin#
-
-
-
-
19
18
17
14
Description
RESERVED
RESERVED
RESERVED
RESERVED (drive to “0”)
PCI5
PCI4
PCI3
PCI2
0
0
0
0
0
0
0
0
-
-
-
-
-
-
-
-
0
0
0
1
1
1
1
1
INTERNATIONAL MICROCIRCUITS, INC. 525 LOS COCHES ST.,
MILPITAS, CA 95035, USA. TEL: 408-263-6300, FAX 408-263-6571
http://www.imicorp.com
Rev 1.2
4/12/2000
Page 7 of 18
CYPRESS [ CYPRESS ]
